Add EmptyScript linter

Add simple linter that checks for `-` markers followed by no code.
Occurrences of these are always a mistake, as they serve no purpose and
code easily be replaced by a blank line.

Change-Id: I1b33a23d3e41bae754cd37fc32ab452f4d5763d4
Reviewed-on: http://gerrit.causes.com/42347
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane.dasilva@brigade.com>